Maintaining Server Performance In A Power Constrained Environment

ABSTRACT

A method of managing resources in a data processing configuration includes allocating system resources to an application to ensure a specified level of performance for the application. A system parameter is then modified to conserve power consumption upon detecting a condition resulting in a reduction of available system power. The original system resource allocation is then modified to maintain the specified level of performance following the modification of the system parameter. The system resources may include system CPU cycles and allocating system resources may include allocating a specified percentage of the CPU cycles to a high priority application. The reduction of available system power may be caused by an excessive ambient temperature or the failure of a power supply. Modifying the system parameter to conserve power consumption includes throttling the CPU speed and then dynamically increasing the percentage of CPU cycles allocated to the high priority application.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation application of and claims priorityfrom U.S. patent application Ser. No. 10/875,253, filed on Jun. 24,2004.

BACKGROUND

1. Field of the Present Invention

The present invention is in the field of data processing systems and,more particularly, data processing systems that employ CPU throttling.

2. History of Related Art

In the field of data processing systems and, more specifically, serversystems, resource management software allows administrators to allocateCPU time to specific applications running under the server's operatingsystem. The resource management software can allocate CPU cycles toapplications such that, for example, high priority applications can beguaranteed a minimum percentage of CPU cycles. This type of resourcemanagement beneficially enables administrators to permit low priorityapplications to execute without substantially degrading the performanceof high priority applications.

Typically, resource management software has been applied in the contextof a static performance environment. More specifically, resourceallocations made by resource management software assume that the CPUspeed is a fixed parameter. The assumption of a constant clock speed,however, is no longer universally accurate. In an effort to addresspower consumption issues, techniques for modifying the CPU clock speedhave emerged. CPU's that execute at slower clock speeds consume lesspower than comparable CPU's running at higher clock speeds. When a CPU'sclock speed is reduced in an effort to conserve power, performanceguarantees based on allocating CPU cycles to high priority applicationsmay require adjustment. Unfortunately, conventional implementations ofsystem manager resources do not account for the potential affect thatCPU throttling may have on performance guarantees (also referred toherein as service level agreements or SLA's). It would be desirable toimplement system management resources that dynamically adjust thefactors required to honor performance guarantees when system conditions,such as available power, change.

SUMMARY OF THE INVENTION

The identified objective is addressed according to the present inventionby a method of managing resources in a data processing configuration.Initially, resources are allocated to an application to ensure aspecified level of performance for the application. A system parameteris then modified to conserve power consumption upon detecting acondition resulting in a reduction of available system power. Theoriginal system resource allocation is then modified to maintain thespecified level of performance following the modification of the systemparameter. The system resources may include system CPU cycles andallocating system resources may include allocating a specifiedpercentage of the CPU cycles to a high priority application. Thereduction of available system power may be caused by an excessiveambient temperature or the failure of a power supply. Modifying thesystem parameter to conserve power consumption includes throttling theCPU speed and then dynamically increasing the percentage of CPU cyclesallocated to the high priority application.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects and advantages of the invention will become apparent uponreading the following detailed description and upon reference to theaccompanying drawings in which:

FIG. 1 is a block diagram of selected elements of a data processingsystem suitable for use with one embodiment of the present invention;

FIG. 2A is a front view of a data processing configuration according toone embodiment of the invention;

FIG. 2B is a rear view of the data processing configuration depicted inFIG. 2A;

FIG. 3 is a flow diagram of a method of adjusting system resourcesaccording to an embodiment of the invention;

FIG. 4 is a flow diagram showing additional detail of one implementationof the method of FIG. 3; and

FIG. 5 is a conceptual representation of selected software elements ofan embodiment of the present invention.

While the invention is susceptible to various modifications andalternative forms, specific embodiments thereof are shown by way ofexample in the drawings and will herein be described in detail. Itshould be understood, however, that the drawings and detaileddescription presented herein are not intended to limit the invention tothe particular embodiment disclosed, but on the contrary, the intentionis to cover all modifications, equivalents, and alternatives fallingwithin the spirit and scope of the present invention as defined by theappended claims.

DETAILED DESCRIPTION OF THE INVENTION

Before describing specific features of a network or server that includesthe dynamic resource allocation features of the present invention,selected elements of a data processing system suitable for use inimplementing the network or server are described. Turning to thedrawings, FIG. 1 illustrates selected features of a data processingsystem 100 suitable for use in a data processing network or serveraccording to one embodiment of the invention. Data processing system 100may be implemented entirely upon a single printed circuit board or“blade.” Thus, data processing system 100 may be referred to herein asserver blade 100. In the depicted embodiment, server blade 100 includesa set of main processors 102A through 102N (generically or collectivelyreferred to as processor(s) 102) that are connected to a system bus 104.A common system memory 106 is accessible to each processor 102 viasystem bus 104. The system memory is typically implemented with avolatile storage medium such as an array of dynamic random access memory(DRAM) devices. The depicted architecture of server blade 100 isfrequently referred to as a symmetric multiprocessor (SMP) systembecause each processor 102 has substantially equal access to systemmemory 106.

In server blade 100, a bus bridge 108 provides an interface betweensystem bus 104 and an I/O bus 110 to which one or more peripheraldevices 114A through 114N (generically or collectively referred to asperipheral device(s) 114) as well as a general purpose I/O (GPIO) port112 are connected. Peripheral devices 114 may include devices such as agraphics adapter, a high-speed network adapter or network interface card(NIC), a hard-disk controller, and the like. I/O bus 110 is typicallycompliant with one of several industry standard I/O bus specificationsincluding, as a common example, the Peripheral Components Interface(PCI) bus as specified in PCI Local Bus Specification Rev 2.2 by the PCISpecial Interest Group (www.pcisig.com).

The depicted embodiment of server blade 100 includes a service processor116 connected to GPIO port 112. Service processor 116 is configured toprovide support for main processors 102. This support may include, forexample, monitoring the power supplied to main processor(s) 102 and, inthe event of a blade crash, initiating a restart of the main processors.

Turning now to FIGS. 2A and 2B, front and rear views respectively of anembodiment of a data processing network or server (generically referredto herein as a data processing configuration) 200 are illustrated. Asshown in the front view of FIG. 2A, data processing configuration 200includes a cabinet (or chassis) 201 having a plurality of slots 202 inits front face 203. Each slot 202 is configured to receive a printedcircuit board-based system such as a server blade 100. (The set ofserver blades depicted in FIG. 2 are identified by reference numerals100 a through 100 n). Each server blade 100 is plugged into aninterconnection (not depicted) referred to herein as the mid-planebecause of its intermediate location between server blades 100 and otheradapters or blades that are plugged into the opposite side of themid-plane from the rear face of cabinet 201 (see FIG. 2B). In thisembodiment, the interconnected server blades 100 in configuration 200are suitable for implementing a local area network (LAN) such as anEthernet LAN in which each blade 100 has its own IP address and MediaAccess Control (MAC) address. Configuration 200 may itself be connectedto an external network such as the Internet through a gateway (notdepicted) or other suitable network device.

The number of server blades within cabinet 201 varies with theimplementation. In a representative configuration, the front face 203 ofcabinet 201 includes 14 or more slots 202 for receiving server blades100. Each server blade 100 is typically a full-height adapter.

The rear view of data processing configuration 200 depicted in FIG. 2Billustrates additional selected elements of the configuration. Morespecifically, the rear face 205 of cabinet 201 includes a set ofhalf-height slots 204. Various half-height modules or blades are pluggedinto the previously mentioned mid-plane via slots 204 in rear face 205.In the depicted embodiment, these modules include a set of networkinterconnect modules identified by reference numerals 210 a, 210 b, 210c, and 210 d, a pair of power supply modules 220 a and 220 b, and firstand second system management modules 120 a and 120 b (generically orcollectively referred to as management module(s) 120). Also shown are aset of cabinet cooling fans 230. It will be appreciated that the numberof network interface modules 210, power supply modules 220, and cabinetcooling fans 230 is implementation specific. Network interface modules210 provide connectivity between the server blades 100 and an externalnetwork such as the Internet. In one embodiment, each server blade 100is configured with four independent network connection paths via thefour separate modules 210 a through 210 d. The power supply modules 220a and 220 b provide configuration 200 with the required voltage levels.

Generally speaking, each management module 120 is configured to monitorand control resources and characteristics of elements of data processingconfiguration 200 that are shared by each server blade 100. Theseresources and characteristics may include, for example, the availablepower, cabinet cooling fans, and environmental characteristics such asthe ambient temperature within cabinet 201. Although multiple andpotentially redundant management modules 120 are depicted, otherimplementations may include just a single management module.

Portions of the present invention may be implemented as a sequence ofprocessor executable instructions (software) for dynamically allocatingsystem resources to maintain service level agreements in the face ofaltered system resources where the instructions are stored on a computerreadable medium. During execution, portions of the software may residein a volatile storage element such as the system memory 106 associatedwith processors 102. At other times, portions of the software may bestored on a non-volatile storage medium such as a floppy diskette, harddisk, CD ROM, DVD, magnetic tape, or other suitable storage medium. Inaddition, portions of the software may be executed by management module120 while other portions are executed by service processors 116 of eachserver blade 100.

Referring to FIG. 5, software elements of an embodiment of the presentinvention are depicted. In the depicted embodiment, data processingconfiguration 200 includes resource management code 502, a resourceallocator code module 504, a CPU throttling code module 506, and a codemodule 508 for monitoring system environment parameters includingambient temperature and power supply status. Resource allocator codemodule 504 enables an administrator to dedicate portions of systemresources on a per-application basis. In one embodiment particularlygermane to the present invention, resource allocator code module 504permits the administrator to implement service level agreements byguaranteeing a specifiable percentage of total CPU cycles on aper-application basis.

CPU throttling code module 506, as its name implies, enables CPUthrottling on data processing configuration 200. CPU throttling refersto deliberately changing the operating frequency of a system's CPU's,typically in an effort to conserve power consumption. Under appropriatestimulus, CPU throttling code module 506 executes commands that effect amodification of the basic clock speed at which the CPU's of dataprocessing configuration 200 are operating. In the most likelyimplementation, the CPU's of data processing configuration 200 arecapable of operating at two or more discreet clock frequencies. CPUthrottling code communicates with operating system code and low levelcode (such as system BIOS) to modify the operating frequency (clockspeed) of the CPU's.

In the implementation depicted in FIG. 5, CPU throttling code module 506communicates with environmental monitoring code module 508.Environmental monitoring code module 508 receives inputs fromenvironmental sensors such as temperature sensors 520 and power supplysensors 530. The power supply sensors 530 provide information about thestatus of the power modules 220 (FIG. 2B) of data processingconfiguration 200 while temperature sensors monitor ambient temperatureand possible the temperature of critical components such as the CPU's.

If environmental monitoring code module 508 receives a sensor inputindicating a condition that reflects or requires a reduction in thepower available to data processing configuration 200, environmentalmonitor code 508 transmits a message to CPU throttling code module 506.CPU throttling code module, in turn, invokes code to slow down the CPU'sof data processing configuration 200.

Resource allocation code module 504 communicates with CPU throttlingcode module 506. In response to detecting a throttling or othermodification of the CPU speed by CPU throttling code module 506,resource allocation code module 504 is configured to evaluate thedetermine, based on the new CPU speed, how best to allocate the CPUcycles to maintain and honor any service level agreements that are inplace. Typically, a reduction in CPU speed requires an increase in theamount of CPU cycles guaranteed to a particular application if theperformance level is to be maintained.

In addition to being enabled to recognize a decrease in available systempower, data processing configuration 200 and code modules 504 and 506are preferably configured to recognize conditions that enable anincrease in available system power. Under such conditions, CPUthrottling code 506 may increase the speed of the CPU's and resourceallocation code module 504 can respond by reducing the percentage of CPUcycles allocated to high priority applications, thereby potentiallyimproving the performance of lower priority applications (withoutadversely impacting the performance level of the high priorityapplications).

Turning now to FIG. 3, a flow diagram of a method 300 of allocatingresources within a system such as data processing configuration 200 ispresented. As depicted in FIG. 3, method 300 is initiated when systemresources such as the CPU resources within data processing configuration200 are allocated (block 302). In accordance with one application of thepresent invention, the allocation of system resources in block 302includes invoking resource management code, most likely implemented in amanagement module 120 of data processing configuration 200 operating inconjunction with agents installed on each server blade 100, to allocateor reserve CPU cycles to at least some applications executing on dataprocessing configuration 200. More specifically, allocation of CPUcycles according to one application of the invention, includessupporting a server level agreement by assigning a specified percentageof total CPU cycles to at least one high priority application.

After allocating system resources as desired, execution of one or moreof the application programs proceeds and one or more system parametersare monitored (block 304). The system parameters being monitored referto parameters that may have an impact on the ability of the system tomaintain the CPU speed at the speed required to support any servicelevel agreements represented by the resource allocations that were madein block 302. These monitored parameters include global, environmentalparameters such as the amount of power available and the operatingtemperature of the data processing configuration 200.

If the monitored parameters are within a specified threshold (asdetermined in block 306), monitoring continues. If the monitoredparameters are no longer within specified limits, a secondary systemparameter is modified (block 307) to address the problem noted with theprimary parameter. If, for example, the monitored parameter isindicative of the available system power, the secondary parametermodified in block 307 may include the operating speed of the CPU's.

In block 308, the resource allocations made in block 302 are adjusteddynamically in response to the modification of the secondary parameter.Preferably, the resource allocations, after adjustment, are sufficientto maintain all existing service level agreements. When the resourceadjusted in block 307 is, for example, achieved by decreasing the speedof the CPU's, the allocation adjustment of block 308 likely includesincreasing the allocation guarantees of high priority applications suchthat high priority applications do not suffer a performance drop-off atthe new CPU speed.

Referring now to FIG. 4, a flow diagram illustrates additional detail ofan implementation of the method 300 depicted in the flow chart of FIG.3. In the implementation depicted in FIG. 4, a method 400 includes theallocation (block 402) of CPU cycles to achieve performance guaranteesor honor service level agreements for a selected set of high priorityapplications, of which there may be one or more. After establishing theCPU allocations required to support the service level agreements underthe initial conditions of the system, the system parameters aremonitored (block 404), most likely by the resource management code orother code executing on the management module(s) 120 of FIG. 2.

The resources monitored in block 404 include the power supply status andthe ambient temperature. Management module 120 monitors status of eachpower supply module 220 in data processing configuration 200. Usinginformation that may be stored in a special purpose, non-volatilestorage element, referred to as vital product data (VPD), managementmodules 120 can determine the aggregate amount of power available ineach power domain. A power domain refers to the resources that receivepower from a common power module 120.

If, in block 406, the monitored temperature is determined to exceed aspecified threshold or, in block 408, the amount of power available isless than a specified threshold, such as when a power supply fails,corrective action is taken. Specifically, the CPU speed is reduced orthrottled (block 420) either to accommodate the lower level of availablepower or to reduce the power consumption in an effort to reduce theoperating temperature. Management modules 120 may determine the maximumCPU speed that can be accommodated at the available level or power. Tomake this determination, the management modules access information thatcorrelates available power and CPU speed. This power/speed informationmay be stored locally within the service processor 116 of each serverblade 100. Alternatively, the power/speed information may be provided asa part of each server's VPD or in some other repository of CPUparameters.

When the resource management module determines that throttling isrequired to accommodate a reduction in available power, managementmodule 120 may inform each service processor 116 of the new CPU speed.Service processors 116, in conjunction with server blade BIOS, willadjust the CPU speed accordingly. The management module 120 will theninform resource management code 502 (FIG. 5) that the blade CPU's havebeen throttled. Returning to FIG. 4, resource management module 502 willthen dynamically reallocate (block 422) CPU cycles to maintain theperformance of high priority applications. In the event that not allhigh priority applications can be accommodated at the lower CPU speeds,resource management code module 502 will notify the user, therebyperhaps prioritizing the correction of the underlying thermal or powersupply problem.

When a failed power supply is replaced or a thermal problem has beenresolved, the environmental monitoring code 508 of FIG. 5 willpreferably detect that the monitored temperature has dropped below aspecified threshold (block 410) or that the available power hasincreased (block 412). In either case, the implication is that dataprocessing configuration 200 can accommodate more power consumption.Accordingly, CPU throttling code module 506 is invoked to increase(block 430) the CPU speed to a level appropriate for the amount ofavailable power and the resource management code module 502 is invokedto re-allocate (block 432) the CPU cycles accordingly.

In the manner described above, the present invention beneficiallyreconciles the ability to allocate resources as needed on aper-application basis with throttling techniques that are typicallyinvoked when power consumption is implicated. The invention extends theusefulness of resource allocation techniques by making the resourceallocation functionality adjustable to environmental conditions of theserver or system. Thus, it will be apparent to those skilled in the arthaving the benefit of this disclosure that the present inventioncontemplates a mechanism for dynamically allocating resources in theface of varying system parameters. It is understood that the form of theinvention shown and described in the detailed description and thedrawings are to be taken merely as presently preferred examples. It isintended that the following claims be interpreted broadly to embrace allthe variations of the preferred embodiments disclosed.

1. A method of managing resources in a data processing system,comprising: allocating system resources to applications executing on theresources to ensure a specified level of performance for at least someof the applications; modifying a system parameter to conserve powerconsumption responsive to a condition resulting in a reduction ofavailable system power; and modifying the allocation of system resourcesto maintain the specified level of performance responsive to modifyingthe system parameter.
 2. The method of claim 1, wherein the systemresources includes system CPU cycles and wherein allocating systemresources includes allocating a specified percentage of the CPU cyclesto a high priority application.
 3. The method of claim 2, wherein thecondition resulting in a reduction of the available system powerincludes a temperature sensor indicating a system temperature in excessof a specified threshold.
 4. The method of claim 2, wherein thecondition resulting in a reduction of the available system powerincludes a power supply failure.
 5. The method of claim 2, whereinmodifying the system parameter to conserve power consumption includesthrottling the CPU speed.
 6. The method of claim 5, wherein modifyingthe allocation of system resources includes increasing the percentage ofCPU cycles allocated to the high priority application responsive to thethrottling.
 7. The method of claim 6, wherein modifying the allocationof system resource further includes decreasing the percentage of CPUcycles allocated to the high priority application responsive toincreasing the CPU speed following a condition indicating an increase inavailable power.
 8. A computer program product comprising a set ofcomputer executable instructions, stored on a computer readable medium,for managing resources in a data processing system, comprising: codemeans for allocating system resources to applications executing on theresources to ensure a specified level of performance for at least someof the applications; code means for modifying a system parameter toconserve power consumption responsive to a condition resulting in areduction of available system power; and code means for modifying theallocation of system resources to maintain the specified level ofperformance responsive to modifying the system parameter.
 9. Thecomputer program product of claim 8, wherein the system resourcesincludes system CPU cycles and wherein the code means for allocatingsystem resources includes code means for allocating a specifiedpercentage of the CPU cycles to a high priority application.
 10. Thecomputer program product of claim 9, wherein the condition resulting ina reduction of the available system power includes a temperature sensorindicating a system temperature in excess of a specified threshold. 11.The computer program product of claim 9, wherein the condition resultingin a reduction of the available system power includes a power supplyfailure.
 12. The computer program product of claim 9, wherein the codemeans for modifying the system parameter to conserve power consumptionincludes throttling the CPU speed.
 13. The computer program product ofclaim 12, wherein the code means for modifying the allocation of systemresources includes code means for increasing the percentage of CPUcycles allocated to the high priority application responsive to thethrottling.
 14. The computer program product of claim 13, wherein thecode means for modifying the allocation of system resources furtherincludes code means for decreasing the percentage of CPU cyclesallocated to the high priority application responsive to increasing theCPU speed following a condition indicating an increase in availablepower.
 15. A data processing system, comprising: means for allocatingresources of the system to a specified application, wherein theallocation of resources to the application reflects an expected level ofperformance associated with the application; means for detecting asystem condition problem; means for modifying a system parameter inresponse to the system condition problem, wherein modification of thesystem parameter affects the ability of the system to maintain theexpected level of performance; and means for re-allocating the systemresources after modifying the system parameter to achieve the expectedlevel of performance.
 16. The system of claim 15, wherein the means forallocating resources includes means for allocating a specifiedpercentage of CPU cycles to the application.
 17. The system of claim 16,wherein means for detecting a system condition problem comprises meansfor detecting a condition that reduces the amount of power available tothe system.
 18. The system of claim 17, wherein modifying a systemparameter comprises reducing the clock speed of at least one processorof the system.
 19. The system of claim 18, wherein re-allocating thesystem resources comprises increasing the percentage of CPU cyclesallocated to the application.
 20. The system of claim 15, wherein thesystem includes a set of blade servers, a power module, and a managementmodule, wherein the set of blade servers shares power supplied by thepower module and wherein the management module participates inallocating resources, modifying the system parameter, and re-allocatingthe system resources.